Add the expression support post processing

[penghuo]

Issue #, if available:
#229
#194
#270
#292

Description of changes:

1.Data Models

The following paragraph describe the BNF grammar for Expression Values.

value             -> collection_value
                     tuple_value
                     scalar_value
                     missing_value
missing_value     -> MISSING
tuple_value       -> {}
                   | {string_value: value (, string_value: value)*}
collection_value  -> [(value)+]
scalar_value      -> string_value
                   | float_value
                   | double_value
                   | integer_value
                   | long_value         

The type of the values are: collection_value, tuple_value, missing_value, scalar_value.

• collection_value is an array could contain duplicated values. It is similar to the JSON array.
• tuple_value is a set of <name, value> pairs.
• missing_value denote the value is missing in the context.
• scalar_value is the core data types defined in SQL

2.BindingTuple

BindingTuple is a set of <bindingName, value>. e.g. Taken the following sample JSON object as example, There are two <bindingName, value> pairs in the BindingTuple. (1) <“integerValue”, integer_value(1)>, (2) <“stringValue”, “string”>.

{
    "integerValue": 1,
    "stringValue":  "string"
}

3.Expression

The following paragraph describe the behavior of the Expression.

// constructors
reference exp    : ExprValue -> Exp
literal exp      : ExprValue -> Exp
unary exp        : Exp       -> Exp
binary exp       : Exp x Exp -> Exp

// observer
valueOf          : Exp x BindingTuple -> ExprValue

Let’s take an example to explain how to construct the expression and evaluate the expression in the BindingTuple context.

// BindingTuple
{
    "a": 1,
    "b": 2
}
// Construct Expression
addExpression = expression(ref("a"), ref("b"))

// valueOf Expression with BindingTuple.
// The evaluation is executed in application order.
addExpression.valueOf(bindingTuple)
-> (+ ref("a").valueOf(bindingTuple) ref("b").valueOf(bindingTuple))
-> (+ 1 2)
-> 3

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[davidcui1225]

LGTM - just 1 minor question

[davidcui1225]

Any specific reason only ABS() and Tan2() were tested against with String values?

[penghuo]

ideally all the type should been tested. the purpose of the test is to verify the error message is as expected.